Those who die in their sleep are often recorded as cases of cardiac failure, but sometimes the real culprit may be sleep apnea, the interruption of breathing during sleep. Researchers injected a cell-specific neurotoxin into a tiny region of the brain stem in rats, the pre-Bötzinger complex, which is essential for breathing. After a few days the rats developed breathing problems, first during REM sleep, then spreading to non-REM sleep and wakefulness. Lapses in breathing rhythm grow more frequent among the elderly and those with neurodegenerative disorders, the researchers note in a Nature Neuroscience report, published online August 7. They speculate that depletion of these neurons from disease or old age results in an increasingly severe apnea from which the body finally cannot rouse itself.